Electrostatic discharge (ESD) is a sudden and momentary electric current that flows between two objects having different electric potentials due to an accumulation of charges. The amount of accumulated charges can vary based on the stored capacitance of an object with respect to another object. All materials are sources of ESD. For example, the human body can store a charge as high as 25,000 volts.
ESD is of particular concern during manufacturing of semiconductor devices. ESD damage can occur for a variety of reasons including, most commonly, through human contact. Other sources of ESD damage include placement of synthetic materials (e.g., plastic, Styrofoam, etc.) on or near electronic equipment and the rapid movement of air near electronic equipment (e.g., due to the use of compressed air to blow dirt off printed circuit boards, placement of circulating fans blowing on electronic equipment, or using an electronic device close to an air handling system). In all of these scenarios, the accumulation of static charges may occur without detection. To make matters worse, direct contact between objects is not required for an ESD event to occur.
There are several steps that semiconductor manufacturers take to prevent ESD damage. For example, they maintain controlled environments including Faraday cages, wrist/foot straps, anti-static mats, conductive flooring material, ion fans, and/or humidity controls. Further, semiconductor devices designs can incorporate built-in ESD protection. However, such measures may not eliminate ESD damage and the resulting manufacturing yield loss.
When a semiconductor device fails, an investigation may be performed to identify whether ESD damage was the cause of the failure. Often, such investigation is unable to identify the source of the failure and, instead, a time-consuming failure analysis may be performed to tear down the device and examine any physical damage for clues as to its source. Yet, determining that physical damage was caused by ESD may still not identify how or when the ESD event occurred. For instance, it may be difficult to determine whether the ESD damaged occurred during manufacturing or after a semiconductor device was delivered to a customer.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.